Occupational exposure to carcinogens and risk of lung cancer: results from The Netherlands cohort study

Our plain-English summary of Occupational exposure to carcinogens and risk of lung cancer: results from The Netherlands cohort study, by A.J. van Loon, I.J. Kant, G.M. Swaen, et al (Occupational and Environmental Medicine, 1997).

The study

• Authors: A.J. van Loon, I.J. Kant, G.M. Swaen, R.A. Goldbohm, A.M. Kremer, P.A. van den Brandt
• Journal: Occupational and Environmental Medicine
• Published: 1997;54(11):817-24
• Cited by: 61 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: To investigate risk of lung cancers associated with common established carcinogenic occupational exposures (asbestos, paint dust, polycyclic aromatic hydrocarbons, and welding fumes) in a prospective cohort study among the general population, and to estimate the proportion of lung cancer cases attributable to these occupational exposures.

Methods: A prospective cohort study on diet, other lifestyle factors, job history, and cancer risk that started in 1986 in The Netherlands on 58,279 men, aged 55-69 years. Based on information about job history obtained from a self-administered questionnaire, case by case expert assessment was carried out to assign to each study subject a cumulative probability of occupational exposure for each carcinogenic exposure. For analysis, a case-cohort approach was used, in which the person-years at risk were estimated from a randomly selected subcohort (n = 1688). After 4.3 years of follow up, 524 lung cancer cases with complete job history were available.

Results: After adjustment for age, each of the other occupational exposures, and for smoking habits and intake of vitamin C, beta-carotene, and retinol, significant associations were found between risk of lung cancer and cumulative probability of occupational exposure to asbestos (relative risk (RR) highest/no exposure = 3.49, 95% confidence interval (95% CI) 1.69 to 7.18, trend P < 0.01 or paint dust (RR highest/no exposure = 2.48, 95% CI 0.88 to 6.97, trend P < 0.01). The population attributable risks (PARs) for the four exposures based on the multivariately adjusted RRs for ever exposed versus never exposed workers were calculated. The PAR of lifetime occupational exposure to asbestos was calculated to be 11.6%.

Conclusions: This prospective cohort study among the general population showed that occupational exposure to asbestos or paint dust is associated with higher RRs for lung cancer. This study shows that after adjustment for smoking and diet about 11.6% of the cases of lung cancer in men is attributable to lifetime occupational exposure to asbestos.

In plain English

This prospective cohort study followed 58,279 Dutch men aged 55 to 69 who answered a 1986 questionnaire on diet, lifestyle and job history. Over 4.3 years, 677 developed lung cancer. The 524 cases and 1,316 of 1,630 random subcohort members who had complete job histories were compared. Experts who did not know who had cancer rated each job for the probability of exposure to asbestos, paint dust, polycyclic aromatic hydrocarbons (PAHs) and welding fumes, combined with years exposed. Results were adjusted for age, the other exposures, smoking, and intake of vitamin C, beta-carotene and retinol. After that adjustment, men in the highest asbestos group had a relative risk of lung cancer of 3.49 (95% CI 1.69 to 7.18) compared with unexposed men. For the highest paint dust group the figure was 2.48 (95% CI 0.88 to 6.97). Welding fumes showed no clear association after adjustment. PAHs showed an unexpected inverse association, which the authors said may be a chance finding. The authors concluded that about 11.6% of male lung cancer cases in the general Dutch population is attributable to lifetime occupational asbestos exposure. The questionnaire could not capture actual exposure concentrations.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Prospective cohort study (The Netherlands Cohort Study), analysed with a case-cohort approach in which person-years at risk were estimated from a random subcohort
• Who was studied: 58,279 men aged 55 to 69 from the general population of The Netherlands. They were enrolled in September 1986 with a 36% response rate and followed for 4.3 years, to December 1990. 677 incident lung cancer cases occurred. Of these, 524 cases (77%) and 1316 of the 1630 eligible subcohort members (81%) had completed job histories.
• Exposure: Occupational exposure to asbestos (fiber type not specified), paint dust, polycyclic aromatic hydrocarbons (PAHs) and welding fumes. Two experts assessed each self-reported job case by case, taking period and company into account, and assigned a probability-of-exposure category. This was multiplied by years exposed to give a cumulative probability of exposure (CPE) for each agent.
• Main results:
  • Asbestos, fully adjusted (age, other occupational exposures, smoking, vitamin C, beta-carotene and retinol): men in the highest cumulative exposure tertile compared with unexposed men had RR 3.49 (95% CI 1.69 to 7.18), with a significant trend (P less than 0.01).
  • Asbestos, adjusted for age only: highest exposure category compared with no occupational asbestos exposure, RR 2.66 (95% CI 1.66 to 4.26).
  • Paint dust, fully adjusted: highest exposure compared with no exposure, RR 2.48 (95% CI 0.88 to 6.97), trend P less than 0.01. The authors noted that smoking and diet seemed to explain part of the higher age-adjusted risk.
  • PAHs: after full adjustment, cumulative exposure became inversely associated with lung cancer (highest compared with no exposure RR 0.28, 95% CI 0.09 to 0.89). The authors said this may be a chance finding.
  • Welding fumes: the association did not substantially change after additional adjustment for smoking and diet. In the fully adjusted analysis, the ever compared with never exposed RR was 0.86 (95% CI 0.46 to 1.58).
  • Ever compared with never exposed to asbestos (fully adjusted): RR 2.49 (95% CI 1.31 to 4.75). 8.8% of the subcohort had ever been exposed to asbestos.
  • Population attributable risk: 11.6% for asbestos and 1.7% for paint dust. For paint dust, the ever compared with never RR was 2.46 (95% CI 1.08 to 5.60). PARs were calculated only for exposures with RR above 1.
• The authors' conclusion: The authors concluded that about 11.6% of all male lung cancer cases in the general Dutch population is attributable to lifetime occupational exposure to asbestos.
• Limitations the authors state:
  • The questionnaire-based job histories did not allow estimation of actual past exposure concentrations. Exposure was expressed only as a probability.
  • The response rate was low (36%). The authors stated that data on demographics, smoking and diet indicated this had not adversely affected the cohort.
  • Job histories were available for only 524 of the 677 cases. The authors considered this number sufficient.
  • Only four common exposures were studied, so the true proportion of lung cancer due to occupational exposure may be higher.
  • The cohort's educational make-up differed from the Dutch population. Exposure may therefore be higher in the cohort, and the true PAR lower.
  • There were too few non-smokers among the cases to compare exposure-related risks between smokers and non-smokers.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Lung Cancer, Cohort Study, Carcinogenic, Habit, Relative Risk, confidence interval, Population Attributable Fraction (PAF).

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